Synthesis of TMBQ with transition metal-containing molecular sieve as catalysts

ABSTRACT

A method of oxidizing trimethylphenol (TMP) to trimethylbenzoquinone (TMBQ) by various molecular sieves containing various transition metals. In this method, TMP, a molecular sieve containing a transition metal in its framework, an oxidant and a solvent are mixed together to form a reaction system. The reaction system reacting at a temperature of about room temperature to 150° C. to obtain TMBQ, and the concentration of TMP is about 5-60% wt.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of Taiwanapplication serial no. 090100156, filed Jan. 3, 2001, the fulldisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of Invention

[0003] The present invention relates to a synthetic method of molecularsieves containing transition metals. More particularly, the presentinvention relates to a synthetic method of a mesoporous molecular sievecontaining Cu and Al in its framework.

[0004] The present invention also relates to a method of oxidizingtrimethylphenol (TMP) to trimethylbenzoquinone (TMBQ) by using molecularsieves, which comprise the molecular sieve containing Cu and Al in itsframework, as catalysts.

[0005] 2. Description of Related Art

[0006] Recently, the global market of Vitamin E has dramaticallyincreased. The main markets are in medical ingredients and nutritionfoods. Since the starting material, i.e.2,3,6-trimethyl-1,4-hydroquinone (TMHQ), is not easily obtained in bulk,the price of Vitamin E is quite high. Therefore, researchers have widelystudied how to efficiently manufacture TMHQ at a lower cost.

[0007] In the past two decades, many chemical processes have beendeveloped to manufacture TMHQ by using TMP as the starting material.Sumitomo Chemical Company uses chlorine gas to chlorinate TMP, thennitric acid is used to oxidize TMP to TMHQ (U.S. Pat. No. 3,932,475).The advantage of this process is that the price of TMP is quite cheap,but one problem is that it produces a lot of pollutants. More than 50 kgof pollutive effluent is produced for every kilogram of TMHQ. [C.Mercier and P. Chabardes, in M. G. Scaros and M. Prunier (Eds.),Catalysis of Organic Reactions, Marcel Decker, New York, 1994, pp.213-221.]

[0008] TMP is oxidized to TMBQ, and then TMBQ is hydrogenated to TMHQ byother patents. Catalysts, which can be used in the oxidation step,include MnO₂ and saturated organic acids (U.S. Pat. No. 3,927,045),inorganic or organic acids of Tl (III) (U.S. Pat. No. 3,910,967),chelating complexes of Co (U.S. Pat. No. 4,250,335), complexes of Fe orMn (U.S. Pat. No. 5,712,416), cupric oxide or cuprous oxide (U.S. Pat.No. 4,491,545), and aqueous solutions (U.S. Pat. No. 4,828,762) orsaturated alcohol solutions (U.S. Pat. No. 5,041,572) of cuproushalide/alkaline metal halide. Generally used catalysts in thehydrogenation step include platinum or palladium supported on zeolitesor aluminum oxide, and hydrogen gas is used to hydrogenate TMBQ to TMHQ(U.S. Pat. Nos. 4,491,545 and 4,828,762).

[0009] Some papers about oxidizing TMP to TMBQ are published, such asIto et al. (S. Ito, K. Aihara, M. Matsumoto, Tetrahedron Lett., 1983,24, 5249), have used many kinds of metal oxides and metal salts ascatalysts, acetic acid and 30% hydrogen peroxide solution arerespectively used as a solvent and an oxidant. They found that the bestreaction result was obtained when RuCl₃ was used as the catalyst. Theyield of TMBQ was up to 90%. Since RuCl₃ is readily soluble in thereaction solution, RuCl₃ is hardly separated from the solution to bereusable. Furthermore, the cost of RuCl₃ is quite high, and thus thismethod is not economic.

[0010] Japanese Shimizu et al. (M. Shimizu, H. Orita, T. Hagakawa, K.Takehira, Tetrahedron Lett., 1989, 30, 471) and Russian Kholdeeva et al.(O. A. Kholdeeva, A. V. Golovin, R. I. Maksimovskaya, I. V. Kozhenikov,J. Mol. Catal., 1992, 75, 235) respectively use hetero-polyacids andacetic acid to be the catalyst and the solvent. When 60% wt. H₂O₂ isused as the oxidant, the yield of TMBQ is the highest (about 80%).However, the consumption of H₂O₂ is very large, and the hetero-polyacidsare too readily soluble in water to be isolated from the reactionsolution to be reused again.

[0011] Dutchman Jansen et al. used hetero-polyacids adsorbed on activecarbons to be the catalyst (J. J. Jansen, H. M. van Neldhuizen, H. vanBekkum, J. Mol. Catal. A, 1996, 107, 241), therefore he hope to increasethe easiness of separating the catalyst from the reaction solution.However, washout of hetero-polyacids adsorbed on active carbons is stilloccurring, thus the practicability is not high.

[0012] The turn over number (TON) of catalysts used in the abovereferences is at most about 4-10. Most oxidation catalysts mentionedabove are soluble in organic solvents or water; therefore solvents areneeded for recycling these oxidation catalysts to extract them from thereaction mixtures. This extraction procedure makes the whole reactionprocess more complicated and it still has a large space to improve.

[0013] The widest used molecular sieve is the zeolite, of which poresize is in the microporous range, i.e. about 0.5-1 nm. Therefore, it'sonly applicable in catalyzing chemical reactions of small molecules.However, the development of mesoporous molecular sieves, of which poresize is about 2-10 nm, has made them applicable in catalyzing chemicalreaction of larger molecules, especially in cracking heavy oil andproduction of drugs and fine chemicals. When transition metal is addedin the molecular sieve, the reaction types that can be catalyzed by themolecular sieve have expanded from acid catalyzed reaction to redoxreaction.

[0014] In the last ten years, molecular sieves containing transitionmetal have been popular to be used in synthesis of TMBQ in order toresolve the problem of recovering catalysts from homogeneous reactionsystems. For example, liquid reaction system using zeolites containingTi or V as catalysts and aqueous solution of H₂O₂ as the oxidant caneffectively oxidize phenol to hydroquinone and catechol (J. S. Reddy, S.Sivasanker and P. Ratnasamy., J.Mol.Catal., 1992, 71, 373 and A. V.Ramaswany, S. Sivasanker and P. Ratnasamy., Micro. Mater., 1994, 2,451). Molecular sieves containing copper ions are used in decomposingNO, and those molecular sieves containing Cu²⁺ are prepared byion-exchange between cations of molecular sieves and Cu²⁺.

SUMMARY OF THE INVENTION

[0015] The invention provides a method of oxidizing trimethylphenol(TMP) to trimethylbenzoquinone (TMBQ).

[0016] In this method, TMP, a molecular sieve containing a transitionmetal in its framework, an oxidant and a solvent are mixed to form areaction system, and the reaction system reacts at a suitabletemperature to obtain TMBQ. The concentration of the TMP is about 5-60%wt. The reaction temperature is about room temperature to about 150° C.,the preferred reaction temperature is about 40-80° C., and the morepreferred temperature is about 50-60° C.

[0017] The molecular sieve that can be used in this invention comprisesa zeolite, a mesoporous molecular sieve of hexagonal or cubic latticestructure, and an aluminophosphate molecular sieve. The transition metaldescribed above can be Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru andW, and the amount of the transitioin metal is about 0.1-10% wt. of themolecular sieve.

[0018] The zeolite described above can be ZSM-5, ZSM-11, Zeolite-Y,Zeolite-X, Zeolite-A or β-zeolite. The mesoporous molecular sievedescribed above comprises MCM-41 and MCM-48, and the preferred ones areMCM-41 containing V or Cu/Al. The aluminophosphate molecular sievedescribed above comprises AlPO₄-5, AlPO₄-8, AlPO₄-11, AlPO₄-31, SAPO-37and VPI-5, and the preferred ones are AlPO₄-5 containing Ti, Co or Cu.

[0019] The oxidant's concentration described above is about 5-60% wt.,and it comprises H₂O₂ or ROOH such as t-BuOOH. If oxygen gas is used asthe oxidant, the O₂ flows into the reaction system at a flow rate of1-20 mL/min.

[0020] The solvent's concentration described above is about 5-60% wt.,and it can be nitrites such as CH₃CN; alcohols such as methanol,ethanol, propanol and butanol; aldehydes such as CH₃CHO and PhCHO; andcarboxylic acids such as acetic acid.

[0021] This invention also provides a method of forming a mesoporousmolecular sieve containing Cu and Al in the framework.

[0022] In this method, a Si-containing compound, a Cu-containingcompound, a Al-containing compound, a template reagent and a solvent aremixed together to obtain a mixing solution. In the mixing solution, theAl/Si molar ratio is between about 0-0.2, the Cu/Si molar ratio isbetween about 0-0.1, and the template reagent/Si molar ratio is betweenabout 0.1-2.

[0023] The Si-containing compound can be an inorganic silicate such aswater glass (sodium silicate), or an organic Si-containing compound suchas tetraethoxysilicate (TEOS). The Cu-containing compound can be aninorganic copper salt such as Cu(NO₃)₂. The Al-containing compound canbe an inorganic aluminate such as sodium aluminate, or an organicAl-containing compound such as triethoxyaluminate ortripropoxyaluminate.

[0024] The template reagent can be a tetraethyl ammonium salt, atetrapropyl ammonium salt, a long-chain-alkyl-trimethyl ammonium salt, acopolymer or combinations thereof. The carbon number of thelong-chain-alkyl-trimethyl ammonium salt is 12-20. The solvent can bewater, methanol, ethanol, propanol, butanol or combinations thereof. Theonly requirement for mixing various solvents is that these solvents canform a single-phase system.

[0025] The pH of the mixing solution is adjusted to about 9-11 when themixing solution's pH is larger than 11, or the mixing solution's pH isadjusted to about 0.1-3 when the mixing solution's pH is 3-9. Theadusting pH step can be accomplished by adding acids such as common usedHCl, HNO₃ or H₂SO₄.

[0026] The mixing solution undergoes a hydrothermal reaction under atemperature of about 80-200° C. for about 1-10 days to form themesoporous molecular sieves. Precipitate is separated from the productsof the hydrothermal reaction, and then it is washed and dried. Theprecipitate is calcined at a temperature of about 500-800° C. to removethe template reagent in the mesoporous molecular sieve's pores.

[0027] It is to be understood that both the foregoing generaldescription and the following detailed description are by example only,and are intended to provide further explanation of the invention asclaimed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] I. Method of Synthesizing Molecular Sieves Containing TransitionMetals

[0029] This invention provides a method of synthesizing analuminosilicate molecular sieve containing transition metals. Thesynthesis steps are as follow:

[0030] 1. Both the silicon-containing compound and thealuminum-containing compound or the solutions of both compounds aremixed together, wherein the Al/Si molar ration is 0 to 0.5. Thesilicon-containing compound can be, for example, an inorganic silicateor an organic Si-containing compound, and the aluminum-containingcompound can be, for example, an inorganic aluminate or an organicAl-containing compound.

[0031] 2. An organic template reagent and a salt of transition metal (M)or solutions thereof are added to the reaction solution of step 1, andthe M/Si molar ratio is 0 to 0.5. The organic template can be, forexample, a tetratethyl ammonium salt, a tetrapropyl ammonium salt, along-chain-alkyl-trimethyl ammonium salt or other surfactants, whereinthe carbon number of the long-chain-alkyl-trimethyl ammonium salt'slong-chain-alkyl group is preferred to be 12 to 20 and more preferred tobe 16.

[0032] 3. A hydrothermal reaction is performed for the resultingsolution of step 2 under a temperature of 80-200° C.

[0033] 4. Precipitate is separated from the resulting solution of step3. The precipitate is washed with water and is then dried.

[0034] 5. The precipitate is calcined under a temperature of about500-800° C. to remove the organic template in the pores of thealuminosilicate molecular sieve.

[0035] This invention also provides another method of synthesizing analuminophosphate molecular sieve. The synthesis steps are as follows:

[0036] 1. Both the phosphorous-containing compound and thealuminum-containing compound or the solutions of both compounds aremixed together, wherein the Al/P molar ration is 0.5 to 1.5. Thephosphorous-containing compound can be, for example, inorganic phosphateor an organic P-containing compound, and the aluminum-containingcompound can be, for example, inorganic aluminate or an organicAl-containing compound.

[0037] 2. A salt of transition metal (M) or a solution thereof are addedto the reaction solution of step 1, and M/Al molar ratio is about 0 to0.5.

[0038] 3. An organic template reagent is added to the resulting solutionof step 2. The organic template can be, for example, dipropyl amine,triethyl amine or tripropyl amine, wherein the preferred organictemplate is triethyl amine.

[0039] 4. A hydrothermal reaction is performed for the resultingsolution of step 3 under a temperature of about 100-250° C.

[0040] 5. Precipitate is separated from the resulting solution of step4. The precipitate is washed with water and is then dried.

[0041] 6. The precipitate is calcined under a temperature of about500-800° C. to remove the organic template in the aluminophosphatemolecular sieve's pores.

[0042] Several kinds of molecular sieves containing transition metalsare synthesized by methods mentioned above. These molecular sievescomprise ZSM-5 (a microporous aluminosilicate zeolite), AlPO₄-5 (amicroporous aluminophosphate molecular sieve), and mseoporous MCM-41.Many molecular sieves containing transition metals are found to havecatalytic activity for oxidizing TMP to TMBQ, especially the MCM-41containing V or Cu/Al. Therefore, MCM-41 containing V or Cu/Al will bethe main examples for discussion described below.

[0043] 1. Synthesis method of MCM-41 containing Cu/Al

[0044] A Si-containing compound, an Al-containing compound, aCu-containing compound, a template reagent and a solvent are mixedtogether to form a mixture solution, wherein 0<Al/Si molar ratio≦0.2,0<Cu/Si molar ratio≦0.1, and 0.1≦template/Si molar ratio≦2. TheSi-containing compound can be, for example, an inorganic silicate suchas water glass, i.e. sodium silicate, or an organic Si-containingcompound such as tetraethoxysilicate (TEOS). The Al-containing compoundcan be, for example, an inorganic aluminate such as sodium aluminate oran organic Al-containing compound such as triethoxyaluminate ortripropoxyaluminate. The Cu-containing compound can be, for example, aninorganic copper salt such as Cu(NO₃)₂. The template reagent can be, forexample, a tetraethyl ammonium salt, a tetrapropyl ammonium salt, along-chain-alkyl-trimethyl ammonium salt, copolymer or combinationsthereof. The preferred carbon number of the long-chain-alkyl-trimethylammonium salt's longest alkyl chain is 12 to 20. The solvent can be, forexample, water, methanol, ethanol, propanol, butanol or combinationsthereof, if the different solvent can be mixed to form a single-phasesystem.

[0045] If pH value of the mixture solution is larger than 11, forexample, when water glass is used as the Si source, the pH of themixture solution is adjusted to about 9-11. If pH value of the mixturesolution is between 3 to 9, for example, when TEOS is used as the Sisource, the pH of the mixture solution is adjusted to about 0.1-3. ThepH adjustment can use acids such as common used HCl, HNO₃ or H₂SO₄.

[0046] The mixture solution undergoes a hydrothermal reaction at atemperature of about 80-200° C. for 1-10 days. Precipitate (i.e. MCM-41molecular sieve) is then separated from the mixture solution, washedwith water and dried. Finally, the precipitate is calcined at apreferred temperature of about 500-800° C. to remove the templatereagent in the pores of MCM-41. A real synthetic example will be givenas follows.

[0047] 4.25 g of Cetyltrimethylammonium bromide (CTMABr) is dissolved in30 g of water to get a template solution. An appropriate amount ofCu(NO₃)₂ is added to 100 mL of water, then the mixture is stirred to geta Cu(NO₃)₂ solution. An appropriate amount of NaAlO₂ is added to 15 g ofwater, then the mixture is stirred for 5 min; 5.33 g of water glass and15 g of water are then added to get a mixed solution of sodium aluminateand sodium silicate. The Cu(NO₃)₂ solution is added to the mixedsolution of sodium aluminate and sodium silicate, the template solutionis then added after stirring for 10 min. After stirring for 5 min, thepH of the resulting solution is adjusted to 9.5 to 10. After 2 days ofstirring, the solution undergoes the hydrothermal reaction at atemperature of about 100° C. for 7 days. Next, after the solution'stemperature is lowered to room temperature, the solution is filtered toget the final powder product. The powder is washed with a large amountof water then it is put into an oven to dry at a temperature of about50° C. Finally, the powder is calcined at a temperature of about 560° C.for 12 hours to get MCM-41 containing Cu/Al in its framework.

[0048] 2. Characterization of MCM-41 containing Cu/Al

[0049] In the X-ray powder diffraction (XRD) spectrum of MCM-41 assynthesized, diffraction peaks at 4.08, 2.37, 2.06 and 1.57 nm ofd-spacing appear, which individually represent the Miller index (100),(110), (200) and (210) diffraction planes of hexagonal crystalstructure. After high-temperature calcining to remove CTMABr in thepores of MCM-41, diffraction peaks in XRD spectrum move toward lowerd-spacing direction, which is accompanied by the occurrence that thefull-line-width at half-maximum (FWHM) of diffraction peaks is decreasedand the intensity of diffraction peaks is increased. This XRD spectrumchange indicates that the structure of MCM-41 is condensed aftercalcination, and therefore the pore size is decreased but the crystalstructure is improving.

[0050] For the MCM-41 with the same Al content but different Cu content,the XRD spectra's diffraction peaks do not show large changes, but theFWHM has increased as the Cu content of MCM-41 has increased. For theMCM-41 with the same Cu content but different Al content, the FWHM ofthe XRD spectra's diffraction peak becomes broader when the Al contentis greater than 3%. When the Al content is greater than 10%, the crystalstructure is poor and the diffraction peaks move to lower d-spacingpositions.

[0051] The XRD spectra's changes show that when Cu and/or Al content isgreater than a certain amount, the framework of MCM-41 is twisted.Therefore, Cu and Al should mostly enter the framework of MCM-41, andthe pores are hexagonally arranged. The MCM-41 as synthesized canmaintain the hexagonal-arranged pore structure after calcination at thetemperature of 560° C.

[0052] Inductive Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES)is used to detect the relative amount of various elements in samples,which are listed in Table 1. The number before “C” in the sample namerepresent the atomic ratio (%) of Cu/Si, and the number before “A” inthe sample name represent the atomic ratio (%) of Al/Si. The Cu/Si ratioof MCM-41 products is usually lower than that of the initial reactionsolutions, which shows that Cu is not entirely incorporated into theframework of MCM-41. As for the sample 0C2A, the Al/Si ratio is higherthan that of the initial reaction solution. It may be that a portion ofskeletal SiO₂ is solubilized in aqueous solution, which makes the Alcontent relatively increase. It is indicated that Al can more easilyreplace skeletal Si than Cu. TABLE 1 ICP-AES analysis results of MCM-41containing Cu/Al. Atomic Ratio of Atomic Ratio of Sample name Cu/Si (%)Al/Si (%) of MCM-41 Reactant Product Reactant Product 0C0A 0 0 0 0 0C2A0 0 2 2.16 1C2A 1 0.83 2 1.35 2C0A 2 1.65 0 0 2C2A 2 1.74 2 1.71

[0053] II. Oxidation Reaction of TMP Catalyzed by a Molecular Sieve in aLiquid-phase Reaction System

[0054] This invention provides a method of oxidizing TMP to produceTMBQ, which is catalyzed by a molecular sieve. This method comprises areaction system, which includes TMP, a molecular sieve containing atransition metal in its framework, an oxidant, and a solvent those aremixed together to undergo a reaction under a suitable temperature toobtain TMBQ. The concentration of TMP is about 5-60% wt. The preferredreaction temperature is about room temperature to about 150° C., and themore preferred reaction temperature is about 40° C. to 80° C.

[0055] The molecular sieve containing a transition metal in theirframework can be, for example, a zeolite, a mesoporous molecular sieveof hexagonal or cubic crystal structure and an aluminophosphatemolecular sieve. The transition metal contained in the framework of themolecular sieve can be, for example, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Nb, Mo, Ru or W, and the content of the transition metal in theframework of the molecular sieve is about 0.1-10% wt. The zeolite canbe, for example, ZSM-5, ZSM-11, Zeolite-Y, Zeolite-X, Zeolite-A orβ-Zeolite. The mesoporous molecular sieve can be, for example, MCM-41(hexagonal crystal structure) or MCM-48 (cubic crystal structure). Thealuminophosphate molecular sieve can be, for example, AlPO₄-5, AlPO₄-8,AlPO₄-11, ALPO₄-31, SAPO-37 or VPI-5 and AlPO₄-5, and those are betterto contain Ti, Co or Cu in their framework.

[0056] The oxidant's concentration is preferred to be about 5-60% wt.and the oxidant can be, for example, H₂O₂ or alkyl peroxide such astert-butylhydroperoxide (t-BuOOH; abbreviated as TBHP). If molecularoxygen is used as the oxidant, it is better to direct about 1-20 mL/minof oxygen into the reaction system.

[0057] The concentration of the solvent is better to be about 5-60% wt.The usable solvent can be nitriles such as methanenitrile (CH₃CN),alcohols such as methanol, ethanol, propanol or butanol, aldehyde suchas ethanal or benzoaldehyde (PhCHO), and carboxylic acids such as aceticacid.

[0058] A working example is described as below. In a three-neck bottle,2 g of a molecular sieve used as a catalyst is added in a solutioncontaining 10 g TMP (the molar ratio of TMP/solvent is 1/5) to form amixture and is then stirred. The mixture in the three-neck bottle isthen refluxed under a temperature of about 30-80° C. Next, an aqueoussolution of H₂O₂ (35% wt.) is added to the mixture and stirred for aperiod of time. The amount of H₂O₂ added is equal to the equivalentnumber of the TMP.

[0059] Gas Chromatography-Flame Ionization Detector (GC-FID) is used toanalyze the products of the reaction described above. A blank testreaction, which doesn't add the molecular sieve, is also preformed tocompare the results of the reaction described above.

[0060] Embodiment 1: Oxidizing TMP to TMBQ by Sample 2C2A

[0061] Using sample 2C2A as the catalyst, CH₃CN as the solvent, and H₂O₂as the oxidant to catalyze the oxidation of TMP to TMBQ at a temperatureof 60° C. The amount of sample 2C2A added is 2 g, the amount of TMPadded is 10 g, the amount of CH₃CN added is 5 times of molar number ofTMP, and the amount of H₂O₂ added is equal to the molar equivalent ofTMP.

[0062] The analysis of the reaction's products is listed in Table 2.From Table 2, the conversion of TMP is more than 60% in the initial 20min. The conversion of TMP is increased as time passes, and theincreasing rate of the conversion is getting slower after 30 min. Theyield of TMBQ is also increased as time passes and reaches a maximum at40 min. TABLE 2 Analysis results of TMP oxidation. Reaction TimeConversion of TMBQ (min) TMP (%) yield (%) Selectivity (%) 20 63.7 46.773.3 30 79.7 50.3 63.1 40 80.5 57.6 71.6

[0063] Embodiment 2: The Effect of Cu/Al Content to the TMP OxidationTABLE 3 The effect of the Cu/Al content to the TMP oxidation MCM-41Conversion of TMBQ As catalyst TMP (%) yield (%) Conversion (%) 0C0A 1.10 0 2C0A 51.7 27.8 53.8 2C1A 60.5 40.6 67.1 2C2A 63.7 46.7 73.3

[0064] Using MCM-41 samples listed in Table 1 as the catalyst tocatalyze TMP oxidation, the molar ratio of the reaction system ofTMP:H₂O₂:CH₃CN is 1:1:3, and 2 g of MCM-41 is added. The reaction timeis 20 min, and the reaction temperature is 60° C. The analysis ofproducts is listed in Table 3.

[0065] From Table 3, when the MCM-41 without Cu and Al (sample 0C0A) isused as the catalyst, only very low conversion of TMP is detected and noTMBQ is produced. But as long as the MCM-41 contains Cu in its framework(sample 2C0A, 2C1A, and 2C2A), the producing of TMBQ is observed. It isindicated that the Cu is the reactive center for oxidizing TMP. FromTable 3, it is also found that the yield of TMBQ can be increased ifMCM-41 contains Al in its framework.

[0066] Embodiment 3: The Effect of Various Preparing Methods and LatticeStructures of Cu-containing Molecular Sieves to TMP Oxidation

[0067] The product analysis of TMP oxidation catalyzed by variouspreparing methods and lattice structures of Cu-containing molecularsieves are listed In Table 4. In Table 4, samples 2C0A, 2C1A, and 2C2Aare the same as those in Table 1, whereas samples 2C0A-imp, 2C1A-imp1,2C2A-imp1, and 2C2A-imp2 are prepared from sample 0C0A in Table 1. Thepreparation method is immersing the sample 0C0A in an aqueous solutionof Cu and/or Al for a period of time such as for 3 hrs, and thendistilling the sample under a vacuum. In Table 4, numbers before C ofthese sample names represent the Cu/Si atomic ratios (%) of each sample,and numbers before A of these sample names represent the Al/Si atomicratios (%).

[0068] Samples 1% Cu-APO-5 and 1% Cu-APO-5 in Table 4 represent that Cuis added in the gel solution for preparing AlPO₄-5, and the amountsadded are individually 1% and 2% of Cu/Si atomic ratio. SampleCu(NO₃)_(2(aq)) means an aqueous solution of Cu(NO₃)₂, and sample Al₂O₃is powder of aluminum oxide.

[0069] From Table 4, if MCM-41 containing Cu is prepared by immersion(2C0A-imp), only trace amounts of TMBQ can be obtained. If MCM-41 isimmersed in aqueous solution of Cu and Al (sample 2C1A-imp1, 2C2A-imp1,and 2C2A-imp2) to be used as the catalyst, the yield of TMBQ can begreatly increased. However, the yield and selectivity of TMBQ catalyzedby sample 2C1A-imp1, 2C2A-imp1, and 2C2A-imp2 is not good as by sample2C0A, 2C1A, and 2C2A, which are prepared from the gel solution that Cuand Al are initially added therein.

[0070] To understand whether the residual sodium ions affect thecatalytic activity of MCM-41 or not, the aluminum source is changed fromNaAlO₂ (samples 2C1A-imp1 and 2C2A-imp1) to Al₂(SO₄)₃ (sample2C2A-imp2). Comparing the reaction results of samples 2C2A-imp1 and2C2A-imp2, no difference between the TMBQ yields is found (22.8 vs.17.3). TABLE 4 The effect of various preparing method and latticestructure of Cu-containing molecular sieves to TMP oxidation Conversionof TMBQ Catalyst TMP (%) Yield (%) Selectivity (%) MCM-41 2C0A 51.7 27.853.8 2C1A 60.5 40.6 67.1 2C2A 63.7 46.7 73.3 MCM-41 immersed in aqueoussolution of 0.01 M Cu(NO₃)₂ 2C0A-imp 53.1 4.3 8.1 MCM-41 immersed inaqueous solution of 0.01 M

Cu(NO₃)₂ and NaAlO₂ 2C1A-imp1 58.7 15.2 25.9 2C2A-imp1 56.2 22.8 40.6MCM-41 immersed in aqueous solution of 0.01 M

Cu(NO₃)₂ and Al₂(SO₄)₃ 2C2A-imp2 64.9 17.3 26.7 AlPO₄-5 1% Cu-APO-5 85.220.4 23.9 2% Cu-APO-5 84.8 30.4 35.8 No molecular sieves addedCu(NO₃)_(2 (aq)) 64.9 5.3 8.2 Al₂O₃ 35.1 0 0

[0071] The amount of catalyst added is 2 g, and the molar ratio ofTMP:H₂O₂:CH₃CN=1:1:3. The reaction time is 20 min, and the reactiontemperature is 60° C.

[0072] Since Cu and Al are in the forms of CuO and Al₂O₃ attaching onthe framework of molecular sieves that are prepared by the immersingmethod, Al₂O₃ and aqueous solution of Cu(NO₃)₂ are also used to catalyzethe TMP oxidation. However, there is no TMBQ produced in the reactioncatalyzed by Al₂O₃. If the molar equivalent number of Cu(NO₃)₂ used isthe same as that of catalyst 2C2A, only a small amount of TMBQ isdetected. This result indicates that Cu²⁺ is the active site of TMPoxidation, and Cu²⁺ and Al³⁺ in the molecular sieve's framework have abetter catalytic activity. That is, the catalytic activity of samples2C0A, 2C1A and 2C2A is not from the Cu²⁺ dissolved in the reactionsolution.

[0073] For the Cu-containing molecular sieves of various latticestructures, TMBQ is also obtained in the reaction catalyzed by AlPO₄-5(samples 1% Cu-APO-5 and 2% Cu-APO-5). However, the selectivity ofAlPO₄-5 is worse than that of MCM-41.

[0074] Embodiment 4: V-containing MCM-41 Catalyze TMP Oxidation TABLE 5V-containing MCM-41 catalyze TMP oxidation TMP:oxidant Conversion ofSelectivity of (molar ratio) Oxidant Solvent TMP (%) TMBQ (%) 1:1 H₂O₂CH₃CN 55 >95 1:2 H₂O₂ CH₃CN 70 >96 1:1 H₂O₂ Acetone 40 >97 1:1 TBHPCH₃CN 50 >15 1:2 TBHP CH₃CN 60 >10

[0075] The amount of catalyst added is 0.05 g, that of TMP added is 0.7g, and that of solvent added is 10 g. The reaction time is 6 hrs, andthe reaction temperature is 60° C.

[0076] From Table 5, when H₂O₂ is used as the oxidant, a very highselectivity of TMBQ, larger than 95%, can be obtained. For the solventused in the reaction system, the effect of methanenitrile (CH₃CN) isbetter than acetone. As for the oxidant used in the reaction system,although a good conversion rate can be obtained by using t-BuOOH toreplace H₂O₂, many by-products are obtained. Besides, when the amount ofoxidant added is more, the conversion rate of TMP is higher. However,the selectivity of TMBQ is not affected much by the amount of oxidantadded.

[0077] Embodiment 5: AlPO₄-5 Containing Various Transition MetalsCatalyzes TMP Oxidation TABLE 6 AlPO₄-5 containing various transitionmetals catalyzes TMP oxidation Conversion of TMBQ Catalyst TMP (%) TONYield (%) Selectivity (%) 1% Ti-APO-5 84 203 78 93 1% V-APO-5 30  73 2583 1% Cr-APO-5 67 162 58 86 1% Mn-APO-5 68 165 59 87 1% Fe-APO-5 61 14851 84 1% Co-APO-5 73 177 65 92 1% Ni-APO-5 42 102 34 81 1% Cu-APO-5 91220 72 79 1% Zn-APO-5 39  94 32 82

[0078] The amount of catalyst added is 2 g, and TMP:H₂O₂:CH₃COOH=10 g:12mL:22 g. The reaction time is 3 hrs, and the reaction temperature is 60°C.

[0079] The product analysis of AlPO₄-5 molecular sieve containingvarious transition metals catalyzing TMP oxidation is listed in Table 6.The M/Si atomic ratio of transition metal (M) in the AlPO₄-5 (Si) isabout 1%. The TMP conversions and the TMBQ yields vary with varioustransition metals, wherein the conversion of TMP catalyzed by 1%Cu-APO-5 is the highest and that by 1% Ti-APO-5 is the second. As forthe yield of TMBQ, 1% Ti-APO5 the highest and 1% Cu-APO-5 the is second.Therefore, the AlPO₄-5 molecular sieve containing Cu or Ti in itsframework is best for converting TMP to TMBQ in Table 6.

[0080] The number of TMBQ molecules produced by each transition metal,i.e. turn over number (TON), is also shown in Table 6. It is indicatedthat samples 1% Cu-APO-5 and 1% Ti-APO-5 have high catalytic activity,since the TON of 1% Cu-APO-5 and 1% Ti-APO-5 are more than 200.

[0081] Embodiment 6: The Effect of Reaction Temperature to TMP OxidationCatalyzed by AlPO4-5 Molecular Sieve Containing Cu in its FrameworkTABLE 7 The effect of temperature to the TMP oxidation TemperatureConversion TMBQ (° C.) (%) Yield (%) Selectivity (%) 25  0  0 — 40 51 4692 50 83 75 90 60 91 72 79 70 100  74 74 95 97 4.0 4.1 110  100  1.10.01

[0082] The amount of 1% Cu-APO-5 added is 0.2 g. TMP:H₂O₂ :CH₃COOH=1.0g:1.2 mL:2.2 g. The reaction time is 3 hrs.

[0083] In Table 7, the 1% Cu-APO-5 is used as the catalyst and sevenreaction temperatures (25, 40, 50, 60, 70, 95 and 100° C.) are used fortesting the temperature effect to the TMP oxidation. From Table 7, it isfound that TMP oxidation can not be processed at 25° C. When thetemperature reaches 40-50° C., the yield of TMBQ is maintained at about72-75%, and the selectivity of TMBQ is more than 90%. When thetemperature is raised to more than 70° C., the effect is increasing theyields of side products and the selectivity of TMBQ is decreased. As fortemperatures above 95° C., a secondary reaction produces side productswith larger molecular weight, and the yield and the conversion of TMBQis further decreased.

[0084] Embodiment 7: The Effect of Various Solvents and Various Oxidantsto the TMP Oxidation

[0085] Sample 2C2A is used as the catalyst to explore the effect ofvarious solvents and oxidants. The solvents used have ethanol (C₂H₅OH),ethanal (CH₃CHO), methanenitrle (CH₃CN) and benzoaldehyde (PhCHO),whereas the oxidants used have hydrogen peroxide (H₂O₂), TBHP (t-BUOOH),oxygen molecule (O₂). The results are listed in Table 8.

[0086] In Table 8, when hydrogen peroxide is used as the oxidant and theC₂H₅OH is used as the solvent, the conversion of TMP is very low. Whenthe hydrogen peroxide is used as the oxidant and the CH₃CHO is used asthe solvent, the conversion of TMP is much higher but the yield of TMBQis very low. However, when the CH₃CN and PhCHO is used as the solvent,both the conversion of TMP and the yield of TMBQ are quite high. If TBHPis used as the oxidant, the higher TMP conversion rate and TMBQ yieldcan be obtained. Therefore, if H₂O₂ or TBHP is used as the oxidant, thesolvent that is better to use is CH₃CN or PhCHO, and PhCHO is evenbetter. If CH₃CN or PhCHO is used as the solvent, the oxidant that isbetter to be used is H₂O₂ or TBHP, and TBHP is even better.

[0087] O₂ is also used as the oxidant here. The reaction is processedunder an O₂ flow rate of about 20 mL/min into the reaction system, wherethe CH₃CN or PhCHO is used as the solvent. TMP conversion of about 40%is detected after 2 hrs when PhCHO is used as the solvent, and theselectivity of TMBQ is about 52%. As the reaction time increases, theTMP conversion and TMBQ yield are also increased. After 6 hrs, the TMPconversion is up to 82.4%, and the TMBQ yield is also up to 54%.However, when CH₃CN is used as the solvent, no TMBQ is detected after 6hrs. Therefore, when the O₂ is used as the oxidant, PhCHO is better tobe used as the solvent. TABLE 8 the effect of various solvents andoxidants to TMP oxidation Reaction TMBQ Solvent Oxident time Conv. (%)TON Yield (%) Select. (%) C₂H₅OH H₂O₂ 20 min 2.0 2.4 0 0 CH₃CHO H₂O₂ 20min 68.0 82 1.3 1.9 CH₃CN H₂O₂ 20 min 63.7 77 46.7 73.3 CH₃CN TBHP 20min 97.8 118 83.2 85.1 CH₃CN O₂ 6 hrs 17.3 21 0 0 PhCHO H₂O₂ 20 min 87.0105 68.7 78.9 PhCHO TBHP 20 min 98.0 118 87.5 89.3 PhCHO O₂ 2 hrs 43.252 22.3 51.6 PhCHO O₂ 4 hrs 71.4 86 40.9 57.3 PhCHO O₂ 6 hrs 82.4 9644.6 54.1

[0088] The amount of the catalyst added is 0.2 g. The molar ratio ofTMP:oxidant (H₂O₂ or TBHP):solvent is 1:1:3. The O₂ flow is 20 mL/min.The reaction temperature is 60° C.

[0089] Embodiment 8: The Catalytic Activity of Regenerate Catalyst

[0090] Samples 2C2A (MCM-41) and 1% Cu-APO-5 (AlPO₄-5) are used as thecatalyst to compare the catalytic activity after catalyst regeneration.The results are listed in Table 9. The method of forming a regeneratedcatalyst is to separate the catalyst from the reaction solution afterthe reaction, then the catalyst is washed by a large amount of water.After washing it with water, the catalyst is dried at room temperatureand calcined at a temperature of about 560° C. for about 6 hrs.

[0091] From Table 9, the regenerated catalyst still has high catalyticactivity. The yield and selectivity of TMBQ is almost the same for thecatalyst before and after the regeneration. It is shown that thecatalyst, i.e. the molecular sieve, can be reused by regeneratingprocess and is very suitable to be used in industry. TABLE 9 The effectof regenerate catalyst to the TMP oxidation TMBQ Catalyst Conversion (%)Yield (%) Selectivity (%) 2C2A^(a) 64 47 73 2C2A^(a) (Regenerate) 59 4372 1% Cu-APO-5^(b) 91 72 79 1% CU-APO-5^(b) 76 61 80 (Regenerate)

[0092] From the preferred embodiments described above, various molecularsieves containing various transition metals, especially for the MCM-41containing Cu and Al, can be used as the catalyst to catalyze theoxidation of TMP to TMBQ with a suitable oxidant and under a suitablecondition. The TMBQ is the main product of TMP's catalytic oxidation.Therefore, compared with other literatures, this invention has thefollowing advantages:

[0093] 1. Turn over number of TMBQ by per catalytic active site ishigher. The turn over number can be up to 200 by using a suitableoxidant and under a suitable reaction condition. Furthermore, the TMBQyield can be up to more than 85%.

[0094] 2. The reaction temperature is lower for the TMP oxidation inthis invention. The reaction temperature is about 30-80° C. The reactiontime needed is also shorter, only about 6-8 hrs.

[0095] 3. Many oxidants are applicable. Even if the most inert oxidant,O₂, also can be used as the oxidant, wherein the turn over number isabout 50. Accordingly, the oxidant can be properly chosen by the priceof raw materials. Therefore, the cost and throughput can be selectivelyadjusted.

[0096] 4. The raw materials for preparing the catalyst are very cheapand the preparation is very easy. Besides, the molecular sieve catalystis reusable. Therefore, the impact to the environment can be reduced tothe lowest level to fulfill the environmental protection requirement andeconomic effect.

[0097] 5. The molecular sieve catalyst is solid. Therefore, theseparation of catalyst and the reaction solution is easy. This makes thecatalyst easily reusable, and the purification of TMBQ is also easier toprocess. As a result, the production cost can be largely reduced.

[0098] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A method of oxidizing trimethylphenol (TMP) totrimethylbenzoquinone (TMBQ), the method comprising: mixing TMP, amolecular sieve containing a transition metal in the framework, anoxidant and a solvent to form a reaction system, the reaction systemreacting at a temperature of about room temperature to about 150° C. toobtain TMBQ.
 2. The method of claim 1, wherein a concentration of theTMP is about 5-60% wt.
 3. The method of claim 1, wherein the molecularsieve comprises zeolite.
 4. The method of claim 3, wherein the zeoliteis selected from the group consisting of ZSM-5, ZSM-11, Zeolite-Y,Zeolite-X, Zeolite-A and β-zeolite.
 5. The method of claim 1, whereinthe molecular sieve comprises a mesoporous molecular sieve withhexagonal or cubic lattice structure.
 6. The method of claim 5, whereinthe mesoporous molecular sieve contains a transition metal and Al in itsframework.
 7. The method of claim 1, wherein the transition metal isabout 0.1-10% wt.of the molecular sieve.
 8. The method of claim 1,wherein the transition metal is selected from the group consisting ofTi, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru and W.
 9. The method ofclaim 1, wherein the concentration of the oxidant is about 5-60% wt. 10.The method of claim 1, wherein the oxidant is selected from the groupconsisting of H₂O₂, ROOH and O₂, and R is an organic group.
 11. Themethod of claim 1, wherein the solvent is selected from the groupconsisting of nitrites, alcohols, aldehydes, and carboxylic acids. 12.The method of claim 1, wherein the temperature is about 40-80° C.
 13. Amethod of forming a mesoporous molecular sieve containing Cu and Al inthe framework, the mesoporous molecular sieve can catalyze the oxidationof trimethylphenol (TMP), comprising: mixing a Si-containing compound, aCu-containing compound, a Al-containing compound, a template reagent anda solvent to obtain a mixing solution, the Al/Si molar ratio beingbetween about 0-0.2, the Cu/Si molar ratio being between about 0-0.1,and the template reagent/Si molar ratio being between about 0.1-2;adjusting the pH of the mixing solution to be about 9-11 when the pH ofthe mixing solution is larger than 11, or adjusting the pH of the mixingsolution to be about 0.1-3 when the pH of the mixing solution is 3-9;performing a hydrothermal reaction under a temperature of about 80-200°C. for about 1-10 days; separating a precipitate from the products ofthe hydrothermal reaction; washing and then drying the precipitate; andcalcining the precipitate to remove the template reagent therein. 14.The method of claim 13, wherein the Si-containing compound is aninorganic silicate or an organic Si-containing compound.
 15. The methodof claim 13, wherein the Al-containing compound is an inorganicaluminate or an organic Al-containing compound.
 16. The method of claim13, wherein the Cu-containing compound comprises an inorganic coppersalt.
 17. The method of claim 13, wherein the template reagent isselected from the group consisting of a tetraethyl ammonium salt, atetrapropyl ammonium salt, a long-chain-alkyl-trimethyl ammonium salt, acopolymer and combinations thereof.
 18. The method of claim 17, whereinthe carbon number of the long-chain-alkyl-trimethyl ammonium salt is12-20.
 19. The method of claim 13, wherein the solvent is selected fromthe group consisting of water, methanol, ethanol, propanol, butanol andcombinations thereof.
 20. The method of claim 13, wherein thetemperature of the calcining step is about 500-800° C.